(1.) Field of the Invention:
The present invention relates to a drive control circuit, and particularly to a drive control circuit for controlling a driving system including a carriage driving motor, a print head and others, which is to be incorporated in an apparatus such as a printer.
(2.) Description of the Prior Art:
In general, drive control circuits for controlling driving systems each including a carriage driving motor, a print head, etc. have been incorporated into apparatus such as printers.
FIG. 2 is a block diagram showing one of such conventional drive control circuits as described above. In the drawing, a ROM 2 is connected to a CPU 1 which performs predetermined control. In addition, a driving system 3 including a carriage driving motor, a print head, etc. is connected to the CPU 1.
Further, a control program for controlling the driving system 3 and a runaway detection program for the prevention of burning or the like which occurs in the driving motor as a result of the runaway of the control program have been written in the ROM 2.
In each of the conventional drive control circuits, when the CPU 1 is first activated, the control program which has been written in the ROM 2 is read and executed by the CPU 1, so that a desired drive control of the driving system 3 is performed.
In addition, when the control program is run out of control owing to some reasons, the runaway detection program in the ROM 2 is executed so as to reset the CPU 1, thereby preventing failure in the driving system 3.
However, in the above-described conventional drive control circuit, when the ROM 2 is in a normal operation, no problem take place. On the other hand, when a malfunction occurs in the ROM 2, as in the case where no ROM 2 is incorporated in the circuit or in the case where the ROM 2 is damaged, the CPU 1 fails to read the control program and the runaway detection program which have already been written in the ROM 2 and hence the runaway detection program cannot be executed properly, thereby failing to perform proper control of the driving system 3, and the driving system 3 still remains energized. As a consequence, the conventional drive control circuit is accompanied by a problem that damage to the driving system 3 caused by burning or the like takes place. Heretofore, a drive control circuit having a protection/control function with respect to the malfunction of the ROM 2 as described above has not been proposed.